KeyEvent¶This event class contains information about key press and release events.
The main information carried by this event is the key being pressed or released. It can be accessed using either GetKeyCode function or GetUnicodeKey. For the printable characters, the latter should be used as it works for any keys, including non-Latin-1 characters that can be entered when using national keyboard layouts. GetKeyCode should be used to handle special characters (such as cursor arrows keys or HOME or INS and so on) which correspond to KeyCode enum elements above the WXK_START constant. While GetKeyCode also returns the character code for Latin-1 keys for compatibility, it doesn’t work for Unicode characters in general and will return WXK_NONE for any non-Latin-1 ones. For this reason, it’s recommended to always use GetUnicodeKey and only fall back to GetKeyCode if GetUnicodeKey returned WXK_NONE meaning that the event corresponds to a non-printable special keys.
While both of these functions can be used with the events of wxEVT_KEY_DOWN , wxEVT_KEY_UP and wxEVT_CHAR types, the values returned by them are different for the first two events and the last one. For the latter, the key returned corresponds to the character that would appear in e.g. a text zone if the user pressed the key in it. As such, its value depends on the current state of the Shift key and, for the letters, on the state of Caps Lock modifier. For example, if A key is pressed without Shift being held down, KeyEvent of type wxEVT_CHAR generated for this key press will return (from either GetKeyCode or GetUnicodeKey as their meanings coincide for ASCII characters) key code of 97 corresponding the ASCII value of a . And if the same key is pressed but with Shift being held (or Caps Lock being active), then the key could would be 65, i.e. ASCII value of capital A .
However for the key down and up events the returned key code will instead be A independently of the state of the modifier keys i.e. it depends only on physical key being pressed and is not translated to its logical representation using the current keyboard state. Such untranslated key codes are defined as follows:
Notice that the first rule applies to all Unicode letters, not just the usual Latin-1 ones. However for non-Latin-1 letters only GetUnicodeKey can be used to retrieve the key code as GetKeyCode just returns WXK_NONE in this case.
To summarize: you should handle wxEVT_CHAR if you need the translated key and wxEVT_KEY_DOWN if you only need the value of the key itself, independent of the current keyboard state.
Another difference between key and int events is that another kind of translation is done for the latter ones when the Control key is pressed: int events for ASCII letters in this case carry codes corresponding to the ASCII value of Ctrl-Latter, i.e. 1 for Ctrl-A, 2 for Ctrl-B and so on until 26 for Ctrl-Z. This is convenient for terminal-like applications and can be completely ignored by all the other ones (if you need to handle Ctrl-A it is probably a better idea to use the key event rather than the int one). Notice that currently no translation is done for the presses of \ , ^ and _ keys which might be mapped to ASCII values from 27 to 31. Since version 2.9.2, the enum values WXK_CONTROL_A - WXK_CONTROL_Z can be used instead of the non-descriptive constant values 1-26.
Finally, modifier keys only generate key events but no int events at all. The modifiers keys are WXK_SHIFT , WXK_CONTROL , WXK_ALT and various WXK_WINDOWS_XXX from KeyCode enum.
Modifier keys events are special in one additional aspect: usually the keyboard state associated with a key press is well defined, e.g. KeyboardState.ShiftDown returns true only if the Shift key was held pressed when the key that generated this event itself was pressed. There is an ambiguity for the key press events for Shift key itself however. By convention, it is considered to be already pressed when it is pressed and already released when it is released. In other words, wxEVT_KEY_DOWN event for the Shift key itself will have MOD_SHIFT in GetModifiers and ShiftDown will return True while the wxEVT_KEY_UP event for Shift itself will not have MOD_SHIFT in its modifiers and ShiftDown will return False.
Tip: You may discover the key codes and modifiers generated by all the keys on your system interactively by running the wxWidgets sample and pressing some keys in it.
Events Emitted by this Class¶Handlers bound for the following event types will receive a KeyEvent parameter.
Note
Not all key down events may be generated by the user. As an example, wxEVT_KEY_DOWN with = key code can be generated using the standard US keyboard layout but not using the German one because the = key corresponds to Shift-0 key combination in this layout and the key code for it is 0 , not = . Because of this you should avoid requiring your users to type key events that might be impossible to enter on their keyboard.
Note
If a key down ( EVT_KEY_DOWN ) event is caught and the event handler does not call event.Skip() then the corresponding int event ( EVT_CHAR ) will not happen. This is by design and enables the programs that handle both types of events to avoid processing the same key twice. As a consequence, if you do not want to suppress the wxEVT_CHAR events for the keys you handle, always call event.Skip() in your wxEVT_KEY_DOWN handler. Not doing may also prevent accelerators defined using this key from working. If a key is maintained in a pressed state, you will typically get a lot of (automatically generated) key down events but only one key up one at the end when the key is released so it is wrong to assume that there is one up event corresponding to each down one. For Windows programmers: The key and int events in wxWidgets are similar to but slightly different from Windows WM_KEYDOWN and WM_CHAR events. In particular, Alt-x combination will generate a int event in wxWidgets (unless it is used as an accelerator) and almost all keys, including ones without ASCII equivalents, generate int events too.
See also
Methods Summary¶| __init__ | Constructor. |
| DoAllowNextEvent | Allow normal key events generation. |
| GetKeyCode | Returns the key code of the key that generated this event. |
| GetPosition | Obtains the position (in client coordinates) at which the key was pressed. |
| GetRawKeyCode | Returns the raw key code for this event. |
| GetRawKeyFlags | Returns the low level key flags for this event. |
| GetUnicodeKey | Returns the Unicode character corresponding to this key event. |
| GetX | Returns the X position (in client coordinates) of the event. |
| GetY | Returns the Y position (in client coordinates) of the event. |
| IsKeyInCategory | Returns True if the key is in the given key category. |
| IsNextEventAllowed | Returns True if DoAllowNextEvent had been called, False by default. |
Properties Summary¶| KeyCode | See GetKeyCode |
| Position | See GetPosition |
| RawKeyCode | See GetRawKeyCode |
| RawKeyFlags | See GetRawKeyFlags |
| UnicodeKey | See GetUnicodeKey |
| X | See GetX |
| Y | See GetY |
Class API¶This event class contains information about key press and release events.
Possible constructors:
Inheritance Diagram
KeyEvent(keyEventType=wxEVT_NULL)
Constructor.
Currently, the only valid event types are wxEVT_CHAR and wxEVT_CHAR_HOOK .
| Parameters: | keyEventType (EventType) – |
|---|
Allow normal key events generation.
Can be called from wxEVT_CHAR_HOOK handler to indicate that the generation of normal events should not be suppressed, as it happens by default when this event is handled.
The intended use of this method is to allow some window object to prevent wxEVT_CHAR_HOOK handler in its parent window from running by defining its own handler for this event. Without calling this method, this would result in not generating wxEVT_KEY_DOWN nor wxEVT_CHAR events at all but by calling it you can ensure that these events would still be generated, even if wxEVT_CHAR_HOOK event was handled.
New in version 2.9.3.
Returns the key code of the key that generated this event.
ASCII symbols return normal ASCII values, while events from special keys such as “left cursor arrow” ( WXK_LEFT ) return values outside of the ASCII range. See KeyCode for a full list of the virtual key codes.
Note that this method returns a meaningful value only for special non-alphanumeric keys or if the user entered a character that can be represented in current locale’s default charset. Otherwise, e.g. if the user enters a Japanese character in a program not using Japanese locale, this method returns WXK_NONE and GetUnicodeKey should be used to obtain the corresponding Unicode character.
Using GetUnicodeKey is in general the right thing to do if you are interested in the characters typed by the user, GetKeyCode should be only used for special keys (for which GetUnicodeKey returns WXK_NONE ). To handle both kinds of keys you might write:
def OnChar(self, event):
keycode = event.GetUnicodeKey()
if keycode != wx.WXK_NONE:
# It's a printable character
wx.LogMessage("You pressed '%c'"%keycode)
else:
# It's a special key, deal with all the known ones:
if keycode in [wx.WXK_LEFT, wx.WXK_RIGHT]:
# move cursor ...
MoveCursor()
elif keycode == wx.WXK_F1:
# give help ...
GiveHelp()
| Return type: | int |
|---|
Obtains the position (in client coordinates) at which the key was pressed.
Returns the raw key code for this event.
The flags are platform-dependent and should only be used if the functionality provided by other KeyEvent methods is insufficient.
Under MSW, the raw key code is the value of wParam parameter of the corresponding message.
Under GTK, the raw key code is the keyval field of the corresponding GDK event.
Under OS X, the raw key code is the keyCode field of the corresponding NSEvent.
| Return type: | int |
|---|
Note
Currently the raw key codes are not supported by all ports, use #ifdef HAS_RAW_KEY_CODES to determine if this feature is available.
Returns the low level key flags for this event.
The flags are platform-dependent and should only be used if the functionality provided by other KeyEvent methods is insufficient.
Under MSW, the raw flags are just the value of lParam parameter of the corresponding message.
Under GTK, the raw flags contain the hardware_keycode field of the corresponding GDK event.
Under OS X, the raw flags contain the modifiers state.
| Return type: | int |
|---|
Note
Currently the raw key flags are not supported by all ports, use #ifdef HAS_RAW_KEY_CODES to determine if this feature is available.
Returns the Unicode character corresponding to this key event.
If the key pressed doesn’t have any character value (e.g. a cursor key) this method will return WXK_NONE . In this case you should use GetKeyCode to retrieve the value of the key.
This function is only available in Unicode build, i.e. when USE_UNICODE is 1.
| Return type: | string |
|---|
Returns the X position (in client coordinates) of the event.
| Return type: | int |
|---|
Returns the Y position (in client coordinates) of the event.
| Return type: | int |
|---|
Returns True if the key is in the given key category.
| Parameters: | category (int) – A bitwise combination of named KeyCategoryFlags constants. |
|---|---|
| Return type: | bool |
New in version 2.9.1.
Returns True if DoAllowNextEvent had been called, False by default.
This method is used by wxWidgets itself to determine whether the normal key events should be generated after wxEVT_CHAR_HOOK processing.
| Return type: | bool |
|---|
New in version 2.9.3.
See GetKeyCode
See GetPosition
See GetRawKeyCode
See GetRawKeyFlags
See GetUnicodeKey